The present invention relates to an operation control method and device for a construction machine for effecting easy and reliable control of complicated operations including operations of working devices and movement of a body of the construction machine.
In the prior art construction machine, power distribution and control for operations of various working devices, attitude setting, position retention, movement of the machine body and operation speed are effected by operating an operating lever, pedal, etc. provided in a cab or near a driving seat in forward and reverse, upward and downward, or right and left directions. In relation to enlargement in scale of the construction machine and for the purposes of improvement in a working efficiency and reduction in fatigue of an operator, the above operations are effected through a boosting mechanism utilizing hydraulic, pneumatic or electric devices.
Recently, execution by human power has been replaced by that by a construction machine, and the construction machine is desired to have an operability suitable for very careful work with quickness, safety and economy without any special skill of the operator.
To satisfy such a desire, it is necessary to provide a control system capable of distributing power according to various working conditions, working loads and operation quantities of the operating lever, etc., retaining a relative working speed ratio among related working devices, and smoothly operating each actuator. The operation of the control system cannot be assured by the ability of the operator only. Therefore, in a construction machine utilizing a hydraulic power, for example, power distribution for operation of the working devices is effected by a pilot hydraulic pressure to be obtained by the operation by the operator, while control operation according to the working conditions, etc. is effected by monitoring a condition of each part of the machine with a pickup or sensor and generating a new electric signal by the operator to obtain a desired operating condition of the machine. In this manner, the control operation of the machine is rendered complex.
Such a control system in the prior are will now be described by way of example of a conventional control signal generating device.
FIG. 6 is a sectional view of an essential part of a hydraulic remote control valve. In general, the remote control valve includes push rods 3a and proportional hydraulic signal generating means 4a at four radial positions equally spaced from each other about an operating lever 2a. When the operating lever 2a is tilted in forward, reverse, right and left directions, one or two of the push rods 3a is/are depressed downwardly. As a result, a spring included in the proportional hydraulic signal generating means 4a is compressed by a moving quantity of the push rods 3a, that is, by a quantity proportional to a tilt angle of the operating lever 2a. As the spring is compressed, a reaction force thereof is increased. At this time, until a hydraulic pressure balancing the increased reaction force is generated, a pressure oil in a hydraulic pressure source 6 is allowed to flow into a hydraulic signal port 10. On the other hand, when the operating lever 2a is returned to a neutral position from the condition where a signal pressure is retained in the hydraulic signal port 10, and the reaction force of the spring in the proportional hydraulic signal generating means 4a is accordingly reduced, the hydraulic signal port 10 is brought into communication with a tank port 7 to reduce the signal pressure.
FIG. 7 is a diagrammatic view of a hydraulic system of the proportional hydraulic signal generating means 4a and 4a'0 located on the right and left sides of the operating lever 2a, showing that a signal pressure proportional to a tilt angle of the operating lever 2a in the right and left directions is transmitted to pilot lines 8 and 8'. FIG. 8 is a characteristic graph showing the relationship between an operating lever stroke S and an signal pressure Pi in the proportional hydraulic signal generating means 4a or 4a'. By utilizing this proportional characteristic, remote control such as control of an operating degree of a hydraulic selector valve, for example, is carried out.
FIG. 9 is a sectional view of an essential part of a conventional device for generating an electric signal proportional to a tilt angle of an operating lever 2b. As similar to the above-mentioned remote control valve, push rods 3b and proportional electric signal generating means 5a associated with the push rods 3b are located at four radial positions about the operating lever 2b. Such a device is called a joy stick. The proportional electric signal generating means 5a is constructed by a potentiometer as shown in FIG. 10. When the operating lever 2b is operated in a certain direction, one or two of the push rods 3b present in this direction is/are moved downwardly, and an internal electric resistance of the proportional electric signal generating means 5a is changed with a change in position of contacts associated with the push rods 3b, thereby changing an electric signal. As shown in FIG. 11, a signal voltage Ei is increased in proportion to an operating lever stroke S. It is a matter of course that this characteristic may be readily modified in such a manner as to reduce the signal voltage Ei in proportion to the operating lever stoke S.
As described above, the remote control hydraulic signal generating devive and the electric signal generating device in the prior art are independent products. The remote control valve is mainly employed for control requiring a strong operating force in a remote control system, while the joy stick is employed for a so-called mechatronic control such that the information of the operating lever stroke is added to an electric signal detected according to an operation and condition of some parts to generate a new electric signal. In this manner, the remote control valve and the joy stick are independently employed, or they are sometimes employed simultaneously. Thus, the construction is complex, and the operation tends to be troublesome.